Through all the travails of the Eurozone in recent years, one thing has always been clear: the single currency is run on German lines and by German rules.
Germany pays the bills, so Berlin calls the shots. But suddenly that acceptance of German dominance is being challenged, first at the European Central Bank, and now in Athens, where a Government is likely to be elected next week with an explicit mandate to challenge the policy of austerity.
The defiance of the ECB, where the two German representatives on the board were outvoted, and the rest went ahead with , may be the most serious. The revolt of the Greeks is, however, the most pressing.
Polls now put the far-left Syriza party, led by the young and persuasive Alexis Tsipras, a full six points clear of the conservative New Democracy party.
Tsipras will win on Sunday, it seems the only question is whether he gets an outright majority, or sufficient allies to form a stable coalition.
If he does as he promises, Greece will tear up its agreements with the EU to cut spending, raise taxes, slash public sector jobs and continue enacting painful labour market reforms. Athens will also renegotiate its huge debts, possibly refusing to repay them.
This, Tsipras says, does not mean leaving the Eurozone. His gamble is that the prospect of a Euro break-up is so serious that - faced with the clear will of the Greek people - Brussels and Berlin will negotiate and do a deal. He may be right.
But what was noticeable at the Syriza rally in central Athens last night were the banners from Spain and Italy claiming that where Greece is leading, they will follow.
Syriza may be the first of the insurgent parties to displace the traditional parties of centre-left and centre-right, but they may not be the last.
The far-left Podemos party in Spain is ahead in the polls there with a general election due at the end of the year. The five-star movement in Italy has not gone away, far from it. Marine Le Pen may soon be at the gates of the Elysée Palace.
And this is a real threat to Germany. Accommodate the Greeks and the rest of Southern Europe, possibly France as well, will come looking for the same concessions.
A leading politician here is keen to remind his fellow countrymen how the ancient Greeks of Athens once treated a weaker neighbour on the island of Melos.
As described by the historian Thucydides, the Melians refused to submit to the far more powerful Athenians, saying it would be ‘unjust’ for Athens to subjugate them. “Justice happens between states of equal power” they were told. “The strong do as they can, and the weak suffer what they must”.
Melos was destroyed, every man of of military age slaughtered.
Will Berlin cut off a defiant Syriza Government at the knees, just to show the rest of the Eurozone that rules are there to be obeyed?
On Monday morning, if the polls are anything like correct, this may no longer be a hypothetical question.